How did we get so fat? Part 1

We have an obesity epidemic in our country, in case you hadn’t noticed.  Over two thirds of American adults are overweight or obese.  But why should we be concerned about this in the middle of a COVID pandemic?  Here’s why.  Obesity and its cousins diabetes and hypertension are three of those “comorbidities” that are causing people to die from COVID when they might have otherwise survived.  Also, when this pandemic is over, the epidemic and its costs and consequences will still be with us.

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I would like us to look hard at what are the causes of this epidemic and consider where some of the blame can be placed.  This may help us in finding a way out.  In this first part we will look at the scope of the problem and how we got here.  In the second part next week we will look at the larger social context and some solutions.

It is difficult to place a starting date on the problem but if we put a stake in at about 1960, then we have had a problem for about 60 years.  At that time about 13% of adults were considered obese.  This would be a body mass index, a ratio of weight to height, over 30.  By 2018, it is now about 42% of Americans in that category and about 30% in the overweight groups with a BMI between 25 and 30.  As a real-life example, for a person 5’8” tall, obesity starts at 197 lbs by this definition.  America has seen a 3-fold increase in this category in the past 60 years. Childhood obesity has also risen.  For children above 6 years old, since the early 1960s the obesity rate has risen from about 4% to nearly 20%.  

Obesity is not evenly spread.  About 50% of Blacks are obese; 42% of Whites are obese, 45% of Hispanics, and 17% of Asian Americans are obese.  We also vary by state, with Mississippi having about 70% more obesity than Colorado.  A more complex picture of obesity emerges when considering sex and race.  Among White men there is little difference in the obesity rate across income groups.  But among Hispanic and Black men and especially among all races of women, obesity is more prevalent among poorer SES classes.  The same basically holds true for education levels, with college educated women of all races having lower prevalence.

Obesity costs about $117 billion a year in direct and indirect costs, about half of that paid by taxpayers.  About 100,000 deaths in the US per year can be attributed to obesity.  The cost of obesity to our nation now exceeds that of smoking.

Dieting, as many of us know, is a lost cause, unless you are in the dieting business.  The global market for dieting products and services has grown to about $255 billion this year.  Of course, this includes the thousands of diet books available, diet foods that one can purchase, drugs one can take, supplements that are available, groups one can pay to join, and counseling one can receive. And probably over two thirds of folks who successfully lose weight will regain it in five years.


So, we Americans are in quite a pickle, but it wasn’t always this way.  We are familiar with the sin of gluttony.  Back when sins were sins this was serious business.  In certain societies obesity and gluttony were associated.  This was not true for every society and every era.  In Europe when class structure was more rigidly in place, it was expected that higher classes would be heavier and have fairer skin.  Both of these traits were associated with not being in the sun working all day and having generous quantities of rich foods.  Famous paintings of nudes from the time show women that would be considered rather large by today’s anorexic standards.  And in some non-European cultures, these perceptions of overweight and obesity in women still persist, including certain Arab cultures, in parts of Africa, and in certain Pacific Island cultures.

How did we get here?  You may be familiar with the concept of calories in and calories out.  If more calories go in as food than come out as physical activity, then weight is gained.  While there is indeed truth in this thermodynamic balance, there are factors inside and outside the body that have driven the dramatic increase in obesity over the last 60 years.  As we parse out apparent causes, we have to think about things that have actually changed over that time period.


Let’s start with two examples.

Genes.  We are now in the genomics age with the full library of the human genome and we have been able to identify at least 76 genes whose mutations can contribute to obesity.  So, are genes responsible for the obesity epidemic?  We humans have had basically the same genes for the past 10,000 years or so including these various obese-prone mutations, and yet we are only getting fluffier in the past century.  While we can show that folks with more of these mutations have a higher risk of obesity, there are still plenty of folks with lots of obese mutations that are normal weight.  These mutations might best be called obesity susceptibility mutations.  They only turn on the fat when they meet various internal cues that are facilitated by external factors like lifestyle and environment.

My second example- diet.  Has this changed over 60 years?  Yes, in fact it has.  Caloric intake has increased from 2880 kcal in 1961 to 3600 kcal in 2013, a 24% increase.  This corresponds to roughly 100 kcal of meat, 100 kcal of sugar, 175 kcal of starchy foods, and 400 kcal of vegetable oil used in snacks and other prepared foods.

Most food in 1960 was home cooked, had less sugar and salt, and few people ate out, especially at fast food restaurants.  Many families ate together.  Today, families rarely eat together, often eat out, and often eat pre-packaged foods and a lot more snack foods and sugary drinks.  Where we eat, what we eat, and how we eat have all changed.  Is it any surprise that our weights have changed?

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Then there are factors in our environment that have changed.  Our pharmacies are dispensing many more diabetes medicines, antidepressants, antipsychotics, and antihypertensives.  Many of these are known to increase weight, not only by their direct effect but also because they put us in better health and better moods.

We are sleeping less than in the past, between one and two hours a night and with much more shift work.  Epidemiologic and experimental work has shown that sleep deprivation adds pounds.

We are exposed to more endocrine disruptors.  These are chemicals that benefit us in some way but have been shown to have untoward effects on health including weight gain.  These include flame retardant polybrominated diphenyl ether (PBDE), and the plasticizer bisphenol A (BPA) and phthalates, DEET the bug repellent, and dioxins.

Air conditioning has increased since the 1960s.  In a counterintuitive way, bringing our homes to a steady 70 degrees or so year-round actually burns less calories.

We all have more screen time than in the past.  In the 60s it was a grainy black and white screen with 13 channels if you were lucky.  Now we have multiple devices for multiple purposes.  Our children spend 5-7 hours a day watching screens big and small.  Research has shown a clear link with obesity.  While watching screens, we are all less likely to be paying attention to the snacking we are doing.  We call this mindless eating.  We are also clearly not outdoors being active.  We are not eating home cooked meals with the family.  Kids see more food commercials and tend to have less sleep and more disrupted sleep.

Now for our diets.  Since 1950 we have consumed about 18% less fiber.  Since the early 1800s we have steadily increased our sugar intake by over a half a pound a year every year.  We now consume about 120 lbs per year or about 1/3 lb per day.  Most of this is in snacks and beverages.  It is amazing to walk into a convenience store and see the huge array of drinks and snacks available.

This problem has come on us slowly.  We can’t really remember a time when half the people we meet in the mall or on the street were too large to be healthy.  We don’t think it is unusual to walk into a gas station/convenience store and find it wall-to-wall with junk food.  Heck, when did gas stations and convenience stores first get married?  When did the size of McDonald’s drinks start to creep up?  We are surrounded by an obese culture that we are immune to.  Next week we will talk about this culture, where it comes from and what to do about it.

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